Joe -
First check your INJ cable, twist both ends with the connectors mated to
wipe up any corrosion.
Normally, a negative DC voltage is sent from the TX to the RX via the
INJ cable to cut off the PreMixer stage when in transceive under XMTR
control. It's a high impedance circuit, so doesn't take much to upset it!
Most likely problem is corrosion on the connectors. Possibly a dirty
switch contact in the TRANSCEIVE switch.
When the TRANSCEIVE switch is in XMTR control, you should see, I think,
-30 VDC or so on the INJ connector. It only takes a few volts to
disable to receiver PTO as the negative voltage is applied via D13 to
the Grid of the PreMixer, cutting off the tube. If the -30 VDC is
there, and exercising the cable connectors didn't fix it, then I'd
suspect D13.
The transmitter PTO is disabled under RCVR control by shorting it's
supply voltage to ground.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs
<www.k4oah.com>
Joe Loverti wrote:
Guys:
My T-4XB and R-4A have been working well together the last few weeks.
But, tonight I noticed an odd problem that I'm hoping is an easy fix.
When I have the transmitter controlling the frequency its PTO has
little effect – I continue to hear the receiver PTO and turning the
receiver PTO knob changes frequency. In fact, I can actually hear both
PTOs on different frequencies, as if both PTOs are working with the
receiver's being the dominant or louder of the two. The SPOT still
works however. This is weird and I've never experienced this before
and it started all of a sudden tonight.
What the heck is going on?
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